According to the recent trend, a radio communication system has an increased service frequency band, and cells having decreased radiuses for high speed data communications and increased telephone traffic. This may cause many problems when applying the existing centralized cellular radio network method as it is. More concretely, a configuration of a radio link has a degraded flexibility due to a fixed location of a base station. This may cause a difficulty in providing efficient communication services in a radio environment where traffic distributions or requested telephone traffic are severely changed.
In order to solve these problems, the next generation radio communication system referred to as LTE-Advanced (Long Term Evolution Advanced) system or E-UTRA (Evolved Universal Terrestrial Radio Access) considers a Multi-Hop relay system. This multi-hop relay system has the following advantages. Firstly, a cell service area may be increased by covering partial shadow areas occurring inside a cell area, and a system capacity may be increased. Furthermore, an initial situation requiring less service is implemented by using a relay. This may reduce the initial installation costs.
In the relay system, a communication channel between a base station and a terminal may be implemented through a direct connection therebetween, or may be implemented in the form of a relay node (RN). Here, the communication channel formed between the base station and the RN is called ‘backhaul’ link. An in-band backhaul method indicates a method for dynamically sharing frequency resources between a backhaul communication and a terminal communication, and an out-band backhaul method indicates a method for separately using frequency resources between a backhaul communication and a terminal communication.
Especially, the in-band backhaul method is preferred since additional frequency resources need not be allocated to a backhaul communication. However, the in-band backhaul method has the following problems. When a relay node transmits data to a terminal and at the same time receives data from a base station, reception interference may occur due to transmission in the same frequency band. Furthermore, in order for the relay node to support transmission and reception at the same time, required is an operation of high complexity to increase installation costs. In case of a transmission from a terminal to a relay node, similar problems occur. In the next-generation wireless communication system, it is important to maintain backward compatibility with the conventional system at a maximum level. Therefore, in the in-band backhaul method, reception interference has to be minimized, and state changes in the conventional system or the conventional terminal have to be minimized.